From Big Medical Encyclopedia

GAS MASKS — individual protection equipment of a respiratory organs, persons and an eye of the person from the harmful impurity which are airborne. By the principle of protective action of P. subdivide on filtering and isolating. To destination distinguish P. army, civil and industrial. There are also special P. for protection of animals.

In the filtering P. the breathing air arrives via the filtruyushche-absorbing device, in Krom it is neutralized as a result of processes adsorptions (see), chemisorption (see. Sorption ), catalysis (see) and filterings (see. Filtering ); expired air is removed to the environment. Use of the filtering P. is allowed at the content in air of oxygen not less than 16 about. % and harmful substances no more than 2%.

Fig. 1. Prokofiev's mask in the put-on look.

Filtering P. used in World War I. Originally it were air-permeable bandages, and then the masks bandages impregnated with «provogazovy» solution — a chemisorbent (wet P.). Prokofiev's mask with polyvalent impregnation (fig. 1) was the most perfect of them. In the summer of 1916 on the front Zelinsky's gas masks with rubber a helmet mask, active coal (dry P.) possessing universal protective action on the basis of absorption of gaseous OV began to arrive. In creation and P.'s improvement the big contribution was made by N. D. Zelinsky, N. A. Shilov, G. V. Hlopin, N. P. Prokofiev.

The modern filtering P. consist of a filtruyushche-pogloshayushchy box and a front part. The antigas bag and additional accessories are included in P.'s package (not misted films, a special pencil for protection of glasses of points from fogging, a membrane of intercoms; in the winter to points insulating cuffs are given). The mass of the filtering gas mask from 0,7 to 2,0 kg.

In the filtruyushche-absorbing box are located the antiaerosol filter (a cardboard with fibrous structure) for purification of inhaled air of poisonous smokes, fogs and dust and the furnace charge consisting of the activated coal catalyst purifying inhaled air of vapors of harmful impurity. Filtruyushche-pogloshchayushchuyu the box can be attached to a front part directly or by means of an elastic connecting tube. In the latter case the filtruyushche-pogloshayushchy box is located in an antigas bag, edges serves at the same time and for storage of the Item.

Front part P. (a mask or a helmet mask) consists of the case, points, valves of a breath and exhalation. It can also turn on devices for negotiating, reception of water and liquid food at the put-on P., and also for work with optical devices. Masks produce three, and a helmet mask — three — five sizes.

Protective properties of a front part estimate (tightness) on coefficient of a suction which at high toxic substances shall be no more than 1 • 10 4  %. The set level of tightness shall be provided taking into account admissible mechanical impact on the head of the person (on conditional rigidity for a front part not higher than 7 kg • c) and duration of operation not less 6th hour. Protective properties of the filtruyushche-absorbing box are estimated by time of protective action, a cut fluctuates of several tens minutes to several tens hours depending on type of a box, a type of toxic agents, their concentration, meteorol. factors, and also from the volume of lung ventilation.

Fig. 2. The army filtering gas mask: 1 — an antigas box (in a section); 2 — the activated coal catalyst; 3 — the antismoke (antiaerosol) filter; 4 — a rubber bung; 5 — a helmet mask; 6 — points in a metal frame; 7 — a valve box; 8 — a connecting (corrugated) tube.
Fig. 3. Civil gas mask (GP-4U): 1 — a front part; 2 — a connecting (corrugated) tube; 3 — an antigas box (in a section); 4 — zig (ribbing); 5 — a navintovanny mouth; 6 — an opening for inhaled air (the direction of the movement of air is specified by shooters); 7 — the activated coal catalyst: 8 — the big mesh cylinder; 9 — the small mesh cylinder; 10 — points; 11 — a valve box; 12 — tapes; 13 — a nazatylnik; 14 — a rubber bung.
Fig. 4. Civil gas mask (GP-5): 1 — an antigas box; 2 — a front part (helmet mask); 3 — not misted films for points a helmet mask; 4 — a bag.
Fig. 5. Children's gas masks (and — DP-6m; — DP-6): 1 — an antigas box; 2 — an opening for intake of air; 3 — a rubber bung; 4 — a connecting (corrugated) tube; 5 — a mask; 6 — points; 7 — a valve box with an exhaling valve; 8 — a nazatylnik; 9 — tapes; 10 — guarantee tapes.
Fig. 6. Children's protective camera: 1 — the protective camera; 2 — an antigas box with bellows for air delivery.
Fig. 7. A helmet for wounded in the head (ShR): 1 — a dense part a helmet mask; 2 — points; 3 — a connecting (corrugated) tube; 4 — a valve box with an exhaling valve; 5 — a parietal part of a helmet; 6 — the wedge-shaped valve; 7 — the obturator; 8 — a loop; 9 — tapes.

Army (fig. 2) and civil (fig. 3 and 4) gas masks are intended for protection of staff of Armed Forces and the population of the country from toxic agents (see), products of nuclear explosion and bacterial aerosols. For children produce children's P. (fig. 5). For protection of children aged up to 1,5 years use the protective camera (fig. 6). Individual protection wounded in the head is provided by means of the filtering P. in a set with a helmet for wounded in the head (ShR), executed in the form of a hood (fig. 7), in combination with any of the available filtering boxes.

Fig. 8. The industrial filtering gas mask: 1 — a helmet mask; 2 — a valve box; 3 — a connecting (corrugated) tube; 4, 14 — navintovanny mouths; 5, 12 — tin lattices; 6 — an antigas box; 7, 9 — a dehumidifier; 8 — hopcalite; 10 — active coal; 11 — the wadded filter; 13 — coil spring; 15 — wire meshs.

Industrial gas masks (fig. 8) are intended for protection against poisonous gases, vapors and aerosols, the airborne production rooms. In them the special filtruyushche-absorbing boxes (elements) providing purification of inhaled air of separate harmful substances or homogeneous groups of substances are used. Boxes of such gas masks depending on their purpose have the corresponding episematic coloration and alphabetic marking. The characteristic of the filtruyushche-absorbing boxes of industrial gas masks is presented in the table. For protection against carbon monoxide use a gopkalitovy cartridge of GP-2, in Krom in the presence of the catalyst hopcalite (the mix MnO 2 and CuO) carbon monoxide is oxidized to carbon dioxide gas.

Fig. 9. Respirator (R-2): 1 — the case; 2 — the respiratory valve; 3 — an exhaling valve; 4 — a nasal clip; 5 — a bridle.

Apply (fig. 9) to protection of a respiratory organs only against aerosols and products of nuclear explosion antidust respirators (see).

Adverse influence of the filtering P. on an organism is caused by decrease in visual acuity and hearing, its respiratory resistance, existence of submask space, and also the squeezing action and the shielding properties a helmet mask. Working capacity in P. can decrease by 15 — 25%.

Respiratory resistance of the filtering P. is perceived as the difficulty of breath overcome by more considerable muscle tension, participating in the act of a breath; at the same time negative intra pulmonary and interpleural pressure increases. In the conditions of quet breathing resistance to a breath makes 15 — 25 mm w.g.; at physical activity it increases to 250 — 350 mm w.g. The most significant effect shows respiratory resistance on function of breath and cardiovascular activity. At resistance more than 200 mm w.g. the decompensation of breath and blood circulation can develop.

Harmful space of P. it is accepted to call submask space, in Krom after an exhalation there is a part of air a lot of carbon dioxide gas and water vapors. Air from this space is added by inhaled and worsens its gas and physical structure, especially at frequent shallow breathing.

Front part P. limits a field of vision, reduces visual acuity, complicates perception of sounds and speech transmission, puts pressure upon vessels and nerve terminations, switches off perception of the environment by the receptor field of face skin and head. At low air temperatures and wind freezing injuries of face skin and a neck are possible.

Putting on on struck and patients of the filtering P. is contraindicated at unconsciousness, pulmonary, nasal and gastric bleedings, pernicious vomiting, spasms, acute cardiovascular and pulmonary insufficiency. It is not recommended to use P. at acute diseases of upper respiratory tracts, diseases with unsharply expressed cardiovascular and pulmonary pathology, nausea, abdominal pains. Struck at evacuation in the situation demanding P.'s use it is necessary to divide into the following groups: capable to independently use P.; P. needing the help at putting on; needing P. with a special front part for wounded in the head; faces with contraindications to use P. (are subject to placement in subjects to collective protection).

Fig. 10. The schematic diagram of the isolating gas mask (IP-4): 1 — the regenerative boss; 2 — a respiratory bag; 3 — the valve of excessive pressure; 4 — a starting briquette.
Fig. 11. Oxygen isolating a gas mask: 7 — the regenerative boss; 2 — connecting (corrugated) hoses; 3 — a valve box; 4 — a helmet mask; 5 — the locking gate; 6 — an oxygen cylinder; 7 — a respiratory bag; 8 — the valve of excessive pressure; 9 — a junction pipe.

The isolating P. apply in the presence in air of the toxic agents which are not detained by the filtering P. at the oxygen content in the atmosphere less than 16 about. %. Besides, the isolating P. are used as respiratory devices during the performance of easily diving works. Breath in them is carried out irrespective of the environment at the expense of a reserve of oxygen and absorption of the carbon dioxide gas which is emitted from an organism. Depending on the principle of ensuring breath distinguish the isolating P. on chemically connected oxygen and on the compressed oxygen (air). In P. of the first type (IP-46, IP-46M, IP-4) a source of oxygen is the regenerative boss containing peroxides of alkali metals. Oxygen is released from peroxides as a result of their chemical interaction with moisture and carbon dioxide gas of expired air. The regenerative boss at the same time performs functions of an absorber of carbon dioxide gas (fig. 10). In P. of the second type (KIP-5, KIP-7, KIP-8) breath is provided at the expense of the compressed oxygen (air) which is in a steel cylinder. Absorption of carbon dioxide gas of expired air is carried out by a special alkaline absorber (fig. 11). Also isolating P. combining regeneration of oxygen with its giving from a cylinder are known. The mass of the isolating gas masks of 4 — 16 kg, time of protective action 1/2 — 4 hours. Their operation is strictly regulated by special instructions which non-compliance can lead to accidents.

During the carrying out gas dangerous technical repair operations use the hose P. consisting of a front part and a hose, on Krom of breathing airs arrives from a pure zone. Radius of action of hose P. fluctuates from 20 to 100 m

of P. store in the closed dry rooms at a temperature not over 25 °, at distance not less than 1 m from heat-radiating devices. In an antigas bag it is forbidden to put any foreign objects. Front parts of the used P. need to be disinfected periodically by wiping their 2% solution of formalin or alcohol, and at absence — to process soap water.

See also Protection against means of war of defeat , Individual means of protection .

Bibliography: V. G. Organization's dialects of gas-rescuing service at the chemical companies, M., 1971; Egorov of II. T., Shlyakhov I. A. and Alabin N. I. Civil protection, M., 1977; Pathology, clinic and therapy at defeats of OB and PB, under the editorship of N. A. Bogdanov, D., 1964; Sergeyev N. V. and Mikhaylov M. I. Individual means of protection, Zhurn. Vsesoyuz. chemical about-va of D. I. Mendeleyev, t. 13, No. 6, page 675, 1968; F and at r about in with to and y N. A. Ocherk of emergence and development of a coal gas mask of N. D. Zelinsky, M., 1952; The X l about and and G. V's N. Military and sanitary bases of antigas business, L., 1930.

R. G. Imangulov.